[0001] This invention relates to a sensor system, for use in a high voltage direct current
(HVDC) network, and to a method of operating a sensor system, for use in a HVDC network.
[0002] It is known to use sensors in a HVDC network to measure the properties of the HVDC
network.
[0003] US 2016/057510 A1 discloses a protected transmission of independent sensor signals.
[0004] While the invention is defined in the independent claims, further aspects of the
invention are set forth in the dependent claims, the drawings and the following description.
[0005] According to a first aspect of the invention, there is provided a sensor system for
use in a high voltage direct current network, the sensor system comprising a plurality
of sensor devices, each sensor device configured to obtain a respective sensor measurement,
wherein the plurality of sensor devices are configured to generate a serial data unit
for transmission to a recipient system, the serial data unit configured to include
the plurality of sensor measurements, the serial data unit further configured to include
a plurality of validity indicators, each validity indicator configured to provide
an individual validity status of a respective one of the plurality of sensor measurements.
[0006] Each sensor measurement may include a single physical measurement or may include
a set of physical measurements arranged serially. For example, a given sensor device
may obtain a sensor measurement that includes a single voltage or current, or a sensor
measurement that includes a set of several voltages and/or currents arranged serially
in a measurement data unit. Namely, each sensor measurement in the serial data unit
may correspond to one or more physical measurements.
[0007] The serial data unit includes a sequence of bits that occurs on a single data line,
and may be in the form of a serial data packet or frame. It will be understood that
a "bit" is an electrical or optical signal processed by a software and/or hardware
module or circuit.
[0008] The use of a serial data unit enables the transmission of a plurality of sensor measurements
from the plurality of sensor devices to the recipient system (such as a HVDC network
controller) at low latency to ensure stability of control of the HVDC network and
its components (such as a converter). However, the integrity of the serial data unit
can be adversely affected by at least one faulty bit arising from bit error, which
may be introduced by noise levels.
[0009] Conventionally a serial data unit includes an error-detecting code, which can be
used to detect whether an error is present in the serial data unit. When an error
is detected in a serial data unit, the entire serial data unit is discarded, and a
new serial data unit has to be transmitted from the plurality of sensor devices to
the recipient system. The discarding of the entire original serial data unit may however
be unacceptable for HVDC applications. This is because discarding the entire original
serial data unit may result in the discarding of useful sensor information, particularly
in relation to time-sensitive circumstances such as a fault occurrence.
[0010] By providing the plurality of validity indicators in the serial data unit, it becomes
possible to discern the individual data quality of each sensor measurement stored
in the serial data unit in order to enable the retrieval of useful sensor information
from a serial data unit that includes at least one error, which in turn may limit
or eliminate the need to transmit a new serial data unit. This has the effect of improving
the reliability and performance of the sensor system.
[0011] In contrast, the aforementioned conventional method of detecting an error in the
serial data unit does not take into account the individual data quality of each sensor
measurement, i.e. the aforementioned conventional method of detecting an error in
the serial data unit is incapable of determining which of the sensor measurements
is invalid.
[0012] The invention is not only scalable to any number of sensor devices in the sensor
system, but also allows the data error rate (i.e. the number of data errors per unit
time) to be controlled independently of the number of sensor devices.
[0013] In the invention, the sensor system further includes a sensor management unit configured
to evaluate each validity indicator to determine whether the corresponding sensor
measurement is either valid or invalid.
[0014] The provision of the sensor management unit allows the evaluation of the individual
data quality of each sensor measurement prior to transmission of the sensor measurements
to the recipient system. This in turn permits the implementation of a suitable data
forwarding strategy to improve the retrieval of useful sensor information from the
serial data unit.
[0015] Optionally the sensor system may further include at least one gateway configured
to be in communication with the plurality of sensor devices. The or each gateway may
include the sensor management unit, and the or each gateway may be configured to be
communicable with the recipient system.
[0016] The sensor management unit is configured to transmit the serial data unit to the
recipient system in response to the sensor management unit determining that none of
the plurality of sensor measurements are invalid.
[0017] The sensor management unit is configured to generate a modified serial data unit
based on the serial data unit subsequent to the sensor management unit evaluating
each validity indicator, and to transmit the modified serial data unit to the recipient
system.
[0018] The modified serial data unit may be configured in a number of ways to improve the
performance of the sensor system.
[0019] The modified serial data unit is configured to include at least one valid sensor
measurement from the serial data unit. Such configuration of the modified serial data
unit enables the recipient system to retrieve useful sensor information in the form
of the or each valid sensor measurement from the modified serial data unit.
[0020] The modified serial data unit may be configured to omit the validity indicators from
the serial data unit. Such configuration of the sensor management unit enables the
reduction of the size of the modified serial data unit, which improves the efficiency
of transmitting the modified serial data unit.
[0021] The sensor management unit is configured to generate the modified serial data unit
based on the serial data unit in response to the sensor management unit determining
that at least one of the plurality of sensor measurements is invalid. Such configuration
of the sensor management unit permits the generation of the modified serial data unit
to be responsive to the determination that at least one of the plurality of sensor
measurements is invalid, so as to improve the retrieval of useful sensor information
from the modified serial data unit.
[0022] The modified serial data unit may be configured to include an error indicator that
identifies the or each invalid sensor measurement. Such configuration of the modified
serial data unit allows the recipient system to easily and accurately identify the
or each invalid sensor measurement, thus making it more straightforward to retrieve
useful sensor information from the modified serial data unit.
[0023] The sensor management unit may be configured to generate the modified serial data
unit by replacing the or each invalid sensor measurement with a or a respective replacement
sensor measurement. Such configuration of the sensor management unit increases the
amount of useful sensor information that can be retrieved from the modified serial
data unit.
[0024] There are a number of ways of obtaining the or the respective replacement sensor
measurement, non-limiting examples of which are described as follows.
[0025] The sensor management unit may be configured to obtain the or the respective replacement
sensor measurement by performing signal processing of at least one of the plurality
of sensor measurements.
[0026] The sensor management unit may be configured to obtain the or the respective replacement
sensor measurement by estimating the or the respective replacement sensor measurement.
[0027] The sensor management unit may be configured to obtain the or the respective replacement
sensor measurement by filtering at least one prior sensor measurement obtained at
an earlier time. The or each prior sensor measurement may be stored in the corresponding
gateway.
[0028] The sensor management unit may be configured to obtain the or the respective replacement
sensor measurement by predicting the or the respective replacement sensor measurement
based on a prediction model and at least one prior sensor measurement obtained at
an earlier time.
[0029] The sensor management unit may be configured to obtain the or the respective replacement
sensor measurement by deriving the or the respective replacement sensor measurement
from a redundant sensor measurement obtained by a corresponding redundant sensor device
and/or by application level redundancy. This allows the direct replacement of an invalid
sensor measurement with an actual sensor measurement obtained from a redundant sensor
device.
[0030] It will be understood that the term "application level redundancy" in the context
of this invention refers to the use of one or more other measurement available in
the application (which in this case is the high voltage direct current network) in
order to obtain the or each redundant sensor measurement.
[0031] For example, if a given sensor measurement is linked to one or more other sensor
measurements at application level, a redundant version of the given sensor measurement
can be obtained by the application level redundancy via the relationship between the
given sensor measurement and the or each other sensor measurement at application level.
Namely, although the sensor devices can be independent of each other, it is the application
that links the sensor measurements together.
[0032] The sensor management unit may be configured to obtain the or the respective replacement
sensor measurement by deriving the or the respective replacement sensor measurement
from at least one valid sensor measurement. For example, the sensor management unit
may be configured to perform a calculation (e.g. extrapolation, interpolation, etc.)
of the or the respective replacement sensor measurement based on one or more valid
sensor measurements.
[0033] The modified serial data unit may be configured to include an error-detecting code,
the error-detecting code configured to provide a validity status of the modified serial
data unit.
[0034] The error-detecting code may be in the form of a validity check sequence number,
such as a cyclic redundancy check (CRC) or a frame checksum sequence (FCS). The provision
of the error-detecting code in the modified serial data allows the recipient system
to evaluate the validity of the modified serial data.
[0035] The modified serial data unit may be configured to include at least one error correction
code, the or each error correction code associated with a or a respective invalid
sensor measurement, the or each error correction code being configured to be usable
to correct an error in the corresponding invalid sensor measurement and/or an error
in at least one of the plurality of validity indicators. The provision of the or each
error correction code in the modified serial data allows the recipient system to correct
the or each invalid sensor measurement and/or at least one of the plurality of validity
indicators.
[0036] According to a second aspect of the invention, there is provided a method of operating
a sensor system, wherein the sensor system is for use in a high voltage direct current
network, the sensor system comprising a plurality of sensor devices, each sensor device
configured to obtain a respective sensor measurement, the method further including
the step of generating a serial data unit for transmission to a recipient system,
the serial data unit configured to include the plurality of sensor measurements, the
serial data unit further configured to include a plurality of validity indicators,
each validity indicator configured to provide an individual validity status of a respective
one of the plurality of sensor measurements.
[0037] The features and advantages of the sensor system of the first aspect of the invention
and its embodiments apply mutatis mutandis to the method of the second aspect of the
invention and its embodiments.
[0038] The method of the invention includes the step of evaluating each validity indicator
to determine whether the corresponding sensor measurement is either valid or invalid.
[0039] The method of the invention includes the step of transmitting the serial data unit
to the recipient system in response to the determination that none of the plurality
of sensor measurements are invalid.
[0040] The method of the invention includes the steps of: generating a modified serial data
unit based on the serial data unit subsequent to the evaluation of each validity indicator;
and transmitting the modified serial data unit to the recipient system.
[0041] In the method of the invention, the modified serial data unit is configured to include
at least one valid sensor measurement from the serial data unit.
[0042] In the method of the invention, the modified serial data unit may be configured to
omit the validity indicators from the serial data unit.
[0043] The method of the invention includes the step of generating the modified serial data
unit based on the serial data unit in response to the determination that at least
one of the plurality of sensor measurements is invalid.
[0044] In the method of the invention, the modified serial data unit may be configured to
include an error indicator that identifies the or each invalid sensor measurement.
[0045] The method of the invention may include the step of generating the modified serial
data unit by replacing the or each invalid sensor measurement with a or a respective
replacement sensor measurement.
[0046] The method of the invention may include the step of obtaining the or the respective
replacement sensor measurement by at least one of:
performing signal processing of at least one of the plurality of sensor measurements;
estimating the or the respective replacement sensor measurement;
filtering at least one prior sensor measurement obtained at an earlier time;
predicting the or the respective replacement sensor measurement based on a prediction
model and at least one prior sensor measurement obtained at an earlier time;
deriving the or the respective replacement sensor measurement from a redundant sensor
measurement obtained by a corresponding redundant sensor device and/or by application
level redundancy;
deriving the or the respective replacement sensor measurement from at least one valid
sensor measurement.
[0047] In the method of the invention, the modified serial data unit may be configured to
include an error-detecting code, the error-detecting code configured to provide a
validity status of the modified serial data unit.
[0048] In the method of the invention, the modified serial data unit may be configured to
include at least one error correction code, the or each error correction code associated
with a or a respective invalid sensor measurement, the or each error correction code
being configured to be usable to correct an error in the corresponding invalid sensor
measurement and/or an error in at least one of the plurality of validity indicators.
[0049] A preferred embodiment of the invention will now be described, by way of a non-limiting
example, with reference to the accompanying drawings in which:
Figures 1 to 3 show schematically communications networks with a star topology, a
bus topology, and a ring topology respectively;
Figure 4 shows a conventional serial data frame;
Figure 5 shows an exemplary serial data frame generated by a sensor system according
to an embodiment of the invention; and
Figure 6 illustrates a flow chart depicting an exemplary data forwarding algorithm
implemented by the sensor system of the invention.
[0050] There is provided a sensor system according to an embodiment of the invention, where
the sensor system is used in a HVDC network.
[0051] The sensor system comprises a plurality of sensor devices and a gateway G. Each sensor
device (e.g. current sensor, voltage sensor, etc.) is configured to measure a property
of the HVDC network (e.g. current, voltage, etc.). Each sensor device is in communication
with the gateway G, which in turn is configured to be in communication in use with
a recipient system C, such as a HVDC network controller (e.g. a converter controller).
[0052] In this manner the plurality of sensor devices, the gateway G and the recipient system
C define a communications network. Examples of communications networks incorporating
the plurality of sensor devices, the gateway G and the recipient system C are shown
in Figures 1 to 3 in which the communications networks have a star topology, a bus
topology, and a ring topology respectively.
[0053] In other embodiments, it is envisaged that the sensor system may include one or more
additional gateways. The or each additional gateway may share the same configuration
as the gateway G so as to provide redundancy to the sensor system.
[0054] In use, each of the plurality of sensor devices obtains a respective sensor measurement
S
1, S
2, S
n corresponding to a property of the HVDC network.
[0055] Each sensor measurement S
1, S
2, S
n may include a single physical measurement or may include a set of physical measurements
arranged serially. For example, a given sensor device may obtain a sensor measurement
S
1, S
2, S
n that includes a single voltage or current, or a sensor measurement S
1, S
2, S
n that includes a set of several voltages and/or currents arranged serially in a measurement
data unit. Namely, each sensor measurement may correspond to one or more physical
measurements.
[0056] When the distance L between the plurality of sensor devices and the gateway G is
not considerably greater than the distance d between the gateway G and the recipient
system C, it is desirable to arrange the plurality of sensor measurements S
1, S
2, S
n in a serial data frame in order to enable the transmission of a plurality of sensor
measurements S
1, S
2, S
n from the plurality of sensor devices to the recipient system C at low latency to
ensure stability of control of the HVDC network and its components.
[0057] Figure 4 shows a conventional serial data frame based on a plurality of sensor measurements
S
1, S
2, S
n. In use, the conventional serial data frame is transmitted to the recipient system
C via the gateway G.
[0058] The trailer of the conventional serial data frame includes an error-detecting code
in the form of a CRC, which is calculated based on all of the sensor measurements
S
1, S
2, S
n in the conventional serial data frame. The error-detecting code is then evaluated,
using a CRC checking algorithm, by the gateway G to determine the validity of the
conventional serial data frame. This is ensure the consistency of sensor information
provided by the plurality of sensor devices to the recipient system C. The CRC may
be replaced by another type of validity check sequence number, such as a FCS.
[0059] The integrity of the conventional serial data frame can be adversely affected by
at least one faulty bit, which results in an erroneous value when the error-detecting
code is evaluated by the recipient system C. When an error is found to be present
in the conventional serial data frame, the entire conventional serial data frame is
discarded by the gateway G on the basis that it contains erroneous sensor information
that cannot be delivered to the recipient system C. It would then be necessary to
transmit a new conventional serial data frame from the plurality of sensor devices
to the recipient system C.
[0060] Although the above conventional approach might be acceptable for delay-tolerant applications
(such as non-real-time computations, digital TV transmission systems, internet communications,
email systems, etc.), the discarding of the entire conventional serial data frame
may however be unacceptable for HVDC applications. This is because discarding the
entire conventional serial data frame may result in the discarding of useful sensor
information, particularly in relation to time-sensitive circumstances such as a fault
occurrence for which the provision of reliable waveform measurements can be important.
[0061] Figure 5 shows an exemplary serial data frame generated by the plurality of sensor
devices in accordance with the invention. In addition to the plurality of sensor measurements
S
1, S
2, S
n, the serial data frame of the invention further includes a plurality of validity
indicators FCS
1, FCS
2, FCS
n, each in the form of a FCS (which may be replaced by another type of validity check
sequence number, such as a CRC).
[0062] Each validity indicator FCS
1, FCS
2, FCS
n is calculated based on a respective one of the plurality of sensor measurements S
1, S
2, S
n, and in this manner is configured to provide an individual validity status of the
corresponding sensor measurement S
1, S
2, S
n. The serial data frame of the invention includes an error-detecting code, in the
form of a CRC, to permit the identification of any errors in the validity indicators
FCS
1, FCS
2, FCS
n
[0063] It will be appreciated that it is optional to include a header and a trailer in the
serial data frame of the invention.
[0064] After the serial data frame of the invention is transmitted from the plurality of
sensor devices to the gateway G, a sensor management unit (not shown) of the gateway
G evaluates each validity indicator FCS
1, FCS
2, FCS
n by calculating a value based on a given sensor measurement S
1, S
2, S
n stored in the serial data frame of the invention and comparing the calculated value
against the corresponding validity indicator FCS
1, FCS
2, FCS
n. If the calculated value and the corresponding validity indicator FCS
1, FCS
2, FCS
n are the same, then the given sensor measurement S
1, S
2, S
n stored in the serial data frame of the invention is determined to be valid. Otherwise,
if the calculated value and the corresponding validity indicator FCS
1, FCS
2, FCS
n are not the same, then the given sensor measurement S
1, S
2, S
n stored in the serial data frame of the invention is determined to be invalid.
[0065] In this manner the provision of the plurality of validity indicators FCS
1, FCS
2, FCS
n in the serial data frame of the invention enables the sensor management unit to discern
the individual data quality of each sensor measurement S
1, S
2, S
n in order to determine whether each sensor measurement S
1, S
2, S
n is either valid or invalid.
[0066] In contrast, the aforementioned conventional method of detecting an error in the
conventional serial data frame does not take into account the individual data quality
of each sensor measurement S
1, S
2, S
n, i.e. the aforementioned conventional method of detecting an error in the conventional
serial data frame is incapable of determining which of the sensor measurements S
1, S
2, S
n is invalid.
[0067] The above evaluation of the validity indicators FCS
1, FCS
2, FCS
n of the serial data frame of the invention permits the gateway to implement a suitable
data forwarding strategy to improve the retrieval of useful sensor information from
the serial data frame.
[0068] When none of the plurality of sensor measurements S
1, S
2, S
n stored in the serial data frame of the invention are determined to be invalid, the
sensor management unit then transmits the serial data frame of the invention to the
recipient system C.
[0069] Optionally the sensor management unit may generate a modified serial data frame by
omitting the validity indicators FCS
1, FCS
2, FCS
n from the serial data frame, and transmit the modified serial data frame to the recipient
system C.
[0070] When at least one sensor measurement S
1, S
2, S
n stored in the serial data frame of the invention is determined to be invalid, the
sensor management unit then generates a modified serial data frame that includes any
valid sensor measurement S
1, S
2, S
n and an error indicator that identifies the or each invalid sensor measurement S
1, S
2, S
n, before transmitting the modified serial data frame to the recipient system C. Such
configuration of the modified serial data frame enables the recipient system C to
not only retrieve useful sensor information in the form of the or each valid sensor
measurement S
1, S
2, S
n from the modified serial data frame, but also easily and accurately identify the
or each invalid sensor measurement S
1, S
2, S
n, thus making it more straightforward to retrieve useful sensor information from the
modified serial data frame.
[0071] Optionally the modified serial data frame may be configured to omit the validity
indicators FCS
1, FCS
2, FCS
n from the serial data frame, so that the size of the modified serial data frame can
be reduced to improve the efficiency of transmitting the modified serial data frame
to the recipient system C.
[0072] To increase the amount of useful sensor information that can be retrieved from the
modified serial data frame, the sensor management unit may generate the modified serial
data frame by replacing the or each invalid sensor measurement S
1, S
2, S
n with a or a respective replacement sensor measurement.
[0073] The or the respective replacement sensor measurement may be obtained by the sensor
management unit through signal processing of at least one of the plurality of sensor
measurements S
1, S
2, S
n. It will be understood that the signal processing strategy may be at least partly
under the control of the recipient system C.
[0074] In an example of signal processing of at least one of the plurality of sensor measurements
S
1, S
2, S
n, the sensor management unit may obtain the or the respective replacement sensor measurement
using application level redundancy. For example, the sensor management unit may perform
an estimated calculation (e.g. extrapolation, interpolation, etc.) of the or the respective
replacement sensor measurement based on one or more valid sensor measurements S
1, S
2, S
n.
[0075] In another example of signal processing of at least one of the plurality of sensor
measurements, the sensor management unit may obtain the or the respective replacement
sensor measurement by filtering at least one prior sensor measurement obtained at
an earlier time and stored in the gateway.
[0076] For example, a given sensor measurement, e.g. S
1(k), may be missing from the serial data frame due to an error in the frame, where
'k' refers to the time instant. Then, if the or each prior sensor measurement S
1(m) for earlier 'm' instants of time is stored in the gateway, the sensor management
unit can obtain a filtered sensor measurement S
1(k) by filtering the or each prior sensor measurement Si(m). An exemplary filtered
signal S
1(k) could be given by S
1(k) = (1/m)
∗ [S
1(k-1) + ... + S
1(k-m)].
[0077] In a further example of signal processing of at least one of the plurality of sensor
measurements, the sensor management unit may obtain the or the respective replacement
sensor measurement by predicting the or the respective replacement sensor measurement
based on a prediction model and at least one prior sensor measurement obtained at
an earlier time and stored in the gateway.
[0078] For example, a given sensor measurement, e.g. S
1(k), may be missing from the serial data frame due to an error in the frame, where
'k' refers to the time instant. Then, if the or each prior sensor measurement S
1(m) for earlier 'm' instants of time is stored in the gateway, the sensor management
unit can obtain a predicted sensor measurement S
1(k) based on a prediction model and the or each prior sensor measurement Si(m). An
exemplary prediction signal S
1(k) could be given by S
1(k) = PredictionModel(S1(k-1), ... ,S1(k-m)). The prediction model may be or may include
a set of mathematical equations that describe the expected evolution of signal S
1 as a function of time and is based on the or each prior sensor measurement Si(m).
[0079] Furthermore the sensor system may include a plurality of redundant sensor devices
(not shown), each of which is configured to measure the same property of the HVDC
network as a respective one of the plurality of sensor devices. This allows the sensor
management unit to obtain the or the respective replacement sensor measurement using
sensor redundancy by deriving the or the respective replacement sensor measurement
from a redundant sensor measurement obtained by a corresponding redundant sensor device.
This allows the direct replacement of an invalid sensor measurement S
1, S
2, S
n with an actual sensor measurement obtained from a redundant sensor device.
[0080] Additionally or alternatively, the sensor management unit may obtain the or the respective
replacement sensor measurement by deriving the or the respective replacement sensor
measurement from a redundant sensor measurement obtained by application level redundancy.
In one example, if a given sensor measurement S
1 is linked to one or more other sensor measurements S
2, S
n at application level via an equation (e.g. S
1 = S
2 + S
n), a redundant version of the given sensor measurement S
1 can be obtained by the application level redundancy via the equation (e.g. S
1(redundant) = S
2 + S
n). In another example, if the sensor measurements S
1, S
2, S
n are voltage measurements in a circuit loop, the sensor measurements S
1, S
2, S
n would be linked via Kirchhoff's voltage law, which can then be used to obtain a redundant
version of any one of the sensor measurements S
1, S
2, S
n.
[0081] Optionally the sensor management unit may calculate an error-detecting code of the
modified serial data frame prior to transmitting the modified serial data to the recipient
system C. The error-detecting code may be in the form of a validity check sequence
number, such as a cyclic redundancy check (CRC) or a frame checksum sequence (FCS).
The provision of the error-detecting code in the modified serial data allows the recipient
system C to evaluate the validity of the modified serial data.
[0082] Further optionally the modified serial data frame may be configured to include at
least one error correction code, where the or each error correction code is associated
with a or a respective invalid sensor measurement S
1, S
2, S
n and/or an error in at least one of the plurality of validity indicators FCS
1, FCS
2, FCS
n. The or each error correction code can be used by the recipient system C to correct
an error in the corresponding invalid sensor measurement S
1, S
2, S
n and/or an error in at least one of the plurality of validity indicators FCS
1, FCS
2, FCS
n.
[0083] The or each error correction code is included in the serial data frame in the form
of one or more redundant bits, which do not add further sensor information but instead
provide a safeguard to recover lost data if needed.
[0084] For example, when a given sensor measurement S
1 is formed of the following serially-arranged binary data bits: [d1 d2 = 1 0], redundancy
bits may be added at each sensor device by using the following expression: r1 = d1,
r2 = XOR(d1, d2), r3=XOR(r1,r2), where XOR(.) is the exclusive-or logical operator.
The following serially-arranged bits [d1 d2 r1 r2 r3] are then transmitted from each
sensor device to the gateway. The sensor management unit checks the validity of the
received data by comparing d1 and r1 (which should match in an error-free case) and
by computing the received value of d1 with the received value of d2.
[0085] In this example, and without loss of generality, it is assumed that only one bit
can fail at a time. When the following serially-arranged binary data bits are generated
as [d1 d2 = 1 0], then the serially-arranged bits transmitted to the gateway would
be: [d1 d2 r1 r2 r3] = [1 0 1 1 0]. If, for example, bit d2 is erroneous, the received
serial data frame takes the form of [d1 d2 r1 r2 r3] = [1 1 1 1 0]. The sensor management
unit can then compute the following validations: d1 = r1 (and hence it can assume
that d1 is correct); XOR(d1,d2) = 0, which is different from the received value of
r2; XOR(r1,r2) = 0, which is equal to the received value of r3, and from this it can
assume no errors have occurred in the redundancy bits. Hence the sensor management
unit can infer that d2 is erroneous, and correct the value of d2 by reversing its
logical value, hence locally producing the data bits [d1 d2] = [1 0] to match the
originally generated data bits. The corrected serial data frame is then transmitted
to the recipient system C without the need for retransmitting data from the sensor
devices to the gateway.
[0086] Figure 6 illustrates a flow chart depicting an exemplary data forwarding algorithm
implemented at the gateway G of the sensor system of the invention.
[0087] Upon reception of a serial data frame at the gateway G, the sensor management unit
evaluates the error-detecting code of the serial data frame to determine whether there
is any error present in the serial data frame.
[0088] If the evaluation of the error-detecting code determines that there are no errors
in the serial data frame, the serial data frame is then forwarded in its entirety
to the recipient system C. The validity indicators FCS
1, FCS
2, FCS
n may optionally be omitted from the forwarded serial data frame.
[0089] If the evaluation of the error-detecting code determines that there is at least one
error in the serial data frame, the sensor management unit then individually evaluates
each validity indicator FCS
1, FCS
2, FCS
n in order to determine whether the corresponding sensor measurement S
1, S
2, S
n is valid or invalid.
[0090] Any valid sensor measurement S
k is stored in a buffer, which is denoted as F[k] in Figure 6, where k = 1, 2, ...,
n. Meanwhile the or each invalid sensor measurement is flagged as erroneous, and in
the embodiments shown is replaced by a replacement sensor measurement Ŝ
k, which is then stored in the buffer F[k], where k = 1, 2, ..., n. Ways of obtaining
a replacement sensor measurement are detailed elsewhere in this patent specification.
[0091] Alternatively (not shown in Figure 6), instead of replacing the or each invalid sensor
measurement S
1, S
2, S
n, the or each invalid sensor measurement S
1, S
2, S
n may be stored in the buffer F[k], and the modified serial data frame is configured
to include an error indicator that identifies the or each invalid sensor measurement
S
1, S
2, S
n.
[0092] After all of the validity indicators FCS
1, FCS
2, FCS
n have been evaluated, the sensor management unit calculates an error-detecting code
of the modified serial data frame, and then transmits the modified serial data frame
F to the recipient system C.
[0093] The sensor system of the invention therefore permits the retrieval of useful sensor
information from a serial data frame that includes at least one error, which in turn
may limit or eliminate the need to transmit a new serial data frame. This has the
effect of improving the reliability and performance of the sensor system. In addition
the invention is not only scalable to any number of sensor devices in the sensor system,
but also allows the frame error rate (i.e. the number of frame errors per unit time)
to be controlled independently of the number of sensor devices.
[0094] It will be appreciated that the serial data frame in the above-described embodiment
of the invention may be replaced by another type of serial data unit, such as a serial
data packet.
1. A sensor system for use in a high voltage direct current network, the sensor system
comprising:
a plurality of sensor devices, each sensor device configured to obtain a respective
sensor measurement (S1, S2, Sn), wherein the plurality of sensor devices are configured to generate a serial data
unit for transmission to a recipient system (C), the serial data unit including the
plurality of sensor measurements (S1, S2, Sn), the serial data unit further including
a plurality of validity indicators (FCS1, FCS2, FCSn), each validity indicator (FCS1, FCS2, FCSn) providing
an individual validity status of a respective one of the plurality of sensor measurements
(S1, S2, Sn); characterised in that the sensor system comprises
a sensor management unit configured:
to evaluate each validity indicator (FCS1, FCS2, FCSn) to determine whether the corresponding sensor measurement (S1, S2, Sn) is either valid or invalid;
to generate a modified serial data unit based on the serial data unit subsequent to
the sensor management unit evaluating each validity indicator (FCS1, FCS2, FCSn) in response to determining that at least one of the plurality of sensor measurements
(S1, S2, Sn) is invalid, wherein the modified serial data unit includes at least one valid sensor
measurement (S1, S2, Sn) from the serial data unit; and
to transmit the modified serial data unit to the recipient system (C);
and in that the sensor management unit is configured to transmit the serial data unit to the
recipient system (C) in response to the sensor management unit determining that none
of the plurality of sensor measurements (S1, S2, Sn) are invalid.
2. A sensor system according to claim 1 wherein each sensor measurement includes a single
physical measurement or includes a set of physical measurements arranged serially.
3. A sensor system according to claim 1 further including at least one gateway (G) configured
to be in communication with the plurality of sensor devices, wherein the or each gateway
includes the sensor management unit, and the or each gateway is configured to be communicable
with the recipient system (C).
4. A sensor system according to claim 1 wherein the modified serial data unit omits the
validity indicators (FCS1, FCS2, FCSn) from the serial data unit.
5. A sensor system according to claim 1 wherein the modified serial data unit includes
an error indicator that identifies the or each invalid sensor measurement (S1, S2, Sn).
6. A sensor system according to claim 1 or claim 5 wherein the sensor management unit
is configured to generate the modified serial data unit by replacing the or each invalid
sensor measurement (S1, S2, Sn) with a or a respective replacement sensor measurement (Ŝk).
7. A sensor system according to claim 6 wherein the sensor management unit is configured
to obtain the or the respective replacement sensor measurement (Ŝ
k) by at least one of:
performing signal processing of at least one of the plurality of sensor measurements
(S1, S2, Sn);
estimating the or the respective replacement sensor measurement (Ŝk);
filtering at least one prior sensor measurement obtained at an earlier time;
predicting the or the respective replacement sensor measurement (Ŝk) based on a prediction model and at least one prior sensor measurement obtained at
an earlier time;
deriving the or the respective replacement sensor measurement (Ŝk) from a redundant sensor measurement obtained by a corresponding redundant sensor
device and/or by application level redundancy;
deriving the or the respective replacement sensor measurement (Ŝk) from at least one valid sensor measurement (S1, S2, Sn).
8. A sensor system according to any one of claims 1 to 7 wherein the modified serial
data unit includes an error-detecting code (CRC), the error-detecting code (CRC) providing
a validity status of the modified serial data unit.
9. A sensor system according to any one of claims 1 to 8 wherein the modified serial
data unit includes at least one error correction code, the or each error correction
code associated with a or a respective invalid sensor measurement (S1, S2, Sn), the or each error correction code being usable to correct an error in the corresponding
invalid sensor measurement (S1, S2, Sn) and/or an error in at least one of the plurality of validity indicators (FCS1, FCS2, FCSn).
10. A method of operating a sensor system, wherein the sensor system is for use in a high
voltage direct current network, the sensor system comprising a plurality of sensor
devices and a sensor management unit, each sensor device configured to obtain a respective
sensor measurement (S
1, S
2, S
n), the method further including the step of generating a serial data unit for transmission
to a recipient system (C), the serial data unit including the plurality of sensor
measurements (S
1, S
2, S
n), the serial data unit further including a plurality of validity indicators (FCS
1, FCS
2, FCS
n), each validity indicator (FCS
1, FCS
2, FCS
n) providing an individual validity status of a respective one of the plurality of
sensor measurements, the method being
characterised in that the sensor management unit evaluates each validity indicator (FCS
1, FCS
2, FCS
n) to determine whether the corresponding sensor measurement (S
1, S
2, S
n) is either valid or invalid, and
in that the sensor management unit:
generates a modified serial data unit based on the serial data unit subsequent to
the sensor management unit evaluating each validity indicator (FCS1, FCS2, FCSn) in response to determining that at least one of the plurality of sensor measurements
(S1, S2, Sn) is invalid, wherein the modified serial data unit includes at least one valid sensor
measurement (S1, S2, Sn) from the serial data unit; and
transmits the modified serial data unit to the recipient system (C) and in that the sensor management unit transmits the serial data unit to the recipient system
(C) in response to the sensor management unit determining that none of the plurality
of sensor measurements (S1, S2, Sn) are invalid.
1. Sensorsystem zur Verwendung in einem Hochspannungsgleichstromnetz, das Sensorsystem
umfassend:
eine Vielzahl von Sensorvorrichtungen, wobei jede Sensorvorrichtung konfiguriert ist,
eine entsprechende Sensormessung (S1, S2, Sn) zu erhalten, wobei die Vielzahl von Sensorvorrichtungen konfiguriert ist, eine serielle
Dateneinheit zur Übertragung an ein Empfangssystem (C) zu erzeugen, wobei die serielle
Datendateneinheit die Vielzahl von Sensormessungen (S1, S2, Sn) beinhaltet, die serielle Datendateneinheit weiter eine Vielzahl von Gültigkeitsindikatoren
(FCS1, FCS2, FCSn) beinhaltet, wobei jeder Gültigkeitsindikator (FCS1, FCS2, FCSn) einen individuellen Gültigkeitsstatus einer entsprechenden der Vielzahl von Sensormessungen
(S1, S2, Sn) bereitstellt;
dadurch gekennzeichnet, dass das Sensorsystem umfasst
eine Sensorverwaltungseinheit, konfiguriert zum:
Auswerten jedes Gültigkeitsindikators (FCS1, FCS2, FCSn) um zu bestimmen, ob die entsprechende Sensormessung (S1, S2, Sn) gültig oder ungültig ist;
Erzeugen einer modifizierten seriellen Dateneinheit basierend auf der seriellen Dateneinheit,
anschließend an das Auswerten jedes Gültigkeitsindikators (FCS1, FCS2, FCSn) durch die Sensorverwaltungseinheit in Antwort auf ein Bestimmen, dass mindestens
eine der Vielzahl von Sensormessungen (S1, S2, Sn) ungültig ist, wobei die modifizierte serielle Dateneinheit mindestens eine gültige
Sensormessung (S1, S2, Sn) von der seriellen Dateneinheit beinhaltet; und
Übertragen der modifizierten seriellen Dateneinheit an das Empfangssystem (C);
und dass die Sensorverwaltungseinheit konfiguriert ist, die serielle Dateneinheit
in Antwort auf ein Bestimmen durch die Sensorverwaltungseinheit, dass keine der Vielzahl
von Sensormessungen (S1, S2, Sn) ungültig ist, an das Empfangssystem (C) überträgt.
2. Sensorsystem nach Anspruch 1, wobei jede Sensormessung eine einzelne physikalische
Messung beinhaltet oder einen Satz physikalischer Messungen, die in Reihe angeordnet
sind, beinhaltet.
3. Sensorsystem nach Anspruch 1, weiter enthaltend mindestens ein Gateway (G), das konfiguriert
ist, mit der Vielzahl von Sensorvorrichtungen in Kommunikation zu sein, wobei das
oder jedes Gateway die Sensorverwaltungseinheit beinhaltet oder das oder jedes Gateway
konfiguriert ist, mit dem Empfangssystem (C) kommunikationsfähig zu sein.
4. Sensorsystem nach Anspruch 1, wobei die modifizierte serielle Dateneinheit die Gültigkeitsindikatoren
(FCS1, FCS2, FCSn) aus der seriellen Dateneinheit weglässt.
5. Sensorsystem nach Anspruch 1, wobei die modifizierte serielle Dateneinheit einen Fehlerindikator
beinhaltet, der die oder jede ungültige Sensormessung (S1, S2, Sn) identifiziert.
6. Sensorsystem nach Anspruch 1 oder Anspruch 5, wobei die Sensorverwaltungseinheit konfiguriert
ist, die modifizierte serielle Dateneinheit durch Ersetzen der oder jeder ungültigen
Sensormessung (S1, S2, Sn) mit einer oder einer entsprechenden Ersatzsensormessung (Ŝk) zu ersetzen.
7. Sensorsystem nach Anspruch 6, wobei die Sensorverwaltungseinheit konfiguriert ist,
die oder die entsprechende Ersatzsensormessung (
Ŝk) zu erhalten durch mindestens eines von:
Durchführen einer Signalverarbeitung von mindestens einer der Vielzahl von Sensormessungen
(S1, S2, Sn);
Schätzen der oder der entsprechenden Ersatzsensormessung (Ŝk);
Filtern mindestens einer früheren Sensormessung, die zu einem früheren Zeitpunkt erhalten
wurde;
Vorhersagen der oder der entsprechenden Ersatzsensormessung (Ŝk) basierend auf einem Vorhersagemodell und mindestens einer früheren Sensormessung,
die zu einem früheren Zeitpunkt erhalten wurde;
Ableiten der oder der entsprechenden Ersatzsensormessung (Ŝk) von einer redundanten Sensormessung, die durch eine entsprechende redundante Sensorvorrichtung
und/oder durch Anwendungsebenenredundanz erhalten wird;
Ableiten der oder der entsprechenden Ersatzsensormessung (Ŝk) von mindestens einer gültigen Sensormessung (S1, S2, Sn).
8. Sensorsystem nach einem der Ansprüche 1 bis 7, wobei die modifizierte serielle Dateneinheit
einen Fehlerdetektionscode (CRC) beinhaltet, wobei der Fehlerdetektionscode (CRC)
einen Gültigkeitsstatus der modifizierten seriellen Dateneinheit bereitstellt.
9. Sensorsystem nach einem der Ansprüche 1 bis 8, wobei die modifizierte serielle Dateneinheit
mindestens einen Fehlerkorrekturcode beinhaltet, wobei der oder jeder Fehlerkorrekturcode
mit einer oder einer entsprechenden ungültigen Sensormessung (S1, S2, Sn). verknüpft ist, wobei der oder jeder Fehlerkorrekturcode verwendbar ist, um einen
Fehler in der entsprechenden ungültigen Sensormessung (S1, S2, Sn) und/oder einen Fehler in dem mindestens einen der Vielzahl von Gültigkeitsindikatoren
(FCS1, FCS2, FCSn) zu korrigieren.
10. Verfahren zum Betreiben eines Sensorsystems, wobei das Sensorsystem zur Verwendung
in einem Hochspannungsgleichstromnetz dient, das Sensorsystem umfassend eine Vielzahl
von Sensorvorrichtungen und eine Sensorverwaltungseinheit, wobei jede Sensorvorrichtung
konfiguriert ist, eine entsprechende Sensormessung (S
1, S
2, S
n) zu erhalten, wobei das Verfahren weiter den Schritt zum Erzeugen einer seriellen
Dateneinheit zur Übertragung an ein Empfangssystem (C) beinhaltet, wobei die serielle
Dateneinheit die Vielzahl von Sensormessungen (S
1, S
2, S
n) beinhaltet, die serielle Datendateneinheit weiter eine Vielzahl von Gültigkeitsindikatoren
(FCS
1, FCS
2, FCS
n) beinhaltet, wobei jeder Gültigkeitsindikator (FCS
1, FCS
2, FCS
n) einen individuellen Gültigkeitsstatus einer entsprechenden der Vielzahl von Sensormessungen
bereitstellt, wobei das Verfahren
dadurch gekennzeichnet ist, dass die Sensorverwaltungseinheit jeden Gültigkeitsindikator (FCS
1, FCS
2, FCS
n) auswertet um zu bestimmen, ob die entsprechende Sensormessung (S
1, S
2, S
n) gültig oder ungültig ist, und dass die Sensorverwaltungseinheit:
eine modifizierte serielle Dateneinheit basierend auf der seriellen Dateneinheit,
anschließend an das Auswerten jedes Gültigkeitsindikators (FCS1, FCS2, FCSn) durch die Sensorverwaltungseinheit in Antwort auf ein Bestimmen, dass mindestens
eine der Vielzahl von Sensormessungen (S1, S2, Sn) ungültig ist, erzeugt, wobei die modifizierte serielle Dateneinheit mindestens eine
gültige Sensormessung (S1, S2, Sn) von der seriellen Dateneinheit beinhaltet; und
die modifizierte serielle Dateneinheit an das Empfangssystem (C) überträgt
und dass die Sensorverwaltungseinheit die serielle Dateneinheit in Antwort auf ein
Bestimmen durch die Sensorverwaltungseinheit, dass keine der Vielzahl von Sensormessungen
(S1, S2, Sn) ungültig ist, an das Empfangssystem (C) überträgt.
1. Système de capteur pour une utilisation dans un réseau de courant continu à haute
tension, le système de capteur comprenant :
une pluralité de dispositifs de capteur, chaque dispositif de capteur étant configuré
pour obtenir une mesure de capteur respective (S
1, S
2, S
n), dans lequel la pluralité de dispositifs de capteur sont configurés pour générer
une unité de données en série pour une transmission à un système destinataire (C),
l'unité de données en série incluant la pluralité de mesures de capteur (S
1, S
2, S
n), l'unité de données en série incluant en outre une pluralité d'indicateurs de validité
(FC5
1, FCS
2, FCS
n), chaque indicateur de validité (FC5
1, FCS
2, FCS
n) fournissant un statut de validité individuel d'une respective de la pluralité de
mesures de capteur (S
1, S
2, S
n) ;
caractérisé en ce que le système de capteur comprend une unité de gestion de capteur configurée pour :
évaluer chaque indicateur de validité (FC51, FCS2, FCSn) pour déterminer si la mesure de capteur correspondante (S1, S2, Sn) est soit valide soit invalide ;
générer une unité de données en série modifiée sur la base de l'unité de données en
série après que l'unité de gestion de capteur a évalué chaque indicateur de validité
(FC51, FCS2, FCSn) en réponse à la détermination qu'au moins une de la pluralité de mesures de capteur
(S1, S2, Sn) est invalide, dans lequel l'unité de données en série modifiée inclut au moins une
mesure de capteur valide (S1, S2, Sn) de l'unité de données en série ; et
transmettre l'unité de données en série modifiée au système destinataire (C) ;
et en ce que l'unité de gestion de capteur est configurée pour transmettre l'unité de données
en série au système destinataire (C) en réponse à l'unité de gestion de capteur déterminant
qu'aucune de la pluralité de mesures de capteur (S1, S2, Sn) n'est invalide.
2. Système de capteur selon la revendication 1, dans lequel chaque mesure de capteur
inclut une seule mesure physique ou inclut un ensemble de mesures physiques agencées
en série.
3. Système de capteur selon la revendication 1, incluant en outre au moins une passerelle
(G) configurée pour être en communication avec la pluralité de dispositifs de capteur,
dans lequel la ou chaque passerelle inclut l'unité de gestion de capteur, et la ou
chaque passerelle est configurée pour pouvoir communiquer avec le système destinataire
(C).
4. Système de capteur selon la revendication 1, dans lequel l'unité de données en série
modifiée omet les indicateurs de validité (FC51, FCS2, FCSn) de l'unité de données en série.
5. Système de capteur selon la revendication 1, dans lequel l'unité de données en série
modifiée inclut un indicateur d'erreur qui identifie la ou chaque mesure de capteur
invalide (S1, S2, Sn).
6. Système de capteur selon la revendication 1 ou la revendication 5, dans lequel l'unité
de gestion de capteur est configurée pour générer l'unité de données en série modifiée
en remplaçant la ou chaque mesure de capteur invalide (S1, S2, Sn) par une mesure de capteur de remplacement ou une mesure de capteur de remplacement
respective (Ŝk).
7. Système de capteur selon la revendication 6, dans lequel l'unité de gestion de capteur
est configurée pour obtenir la mesure de capteur de remplacement ou la mesure de capteur
de remplacement respective (Ŝ
k) par au moins l'une des étapes consistant à :
effectuer un traitement de signal d'au moins une de la pluralité de mesures de capteur
(S1, S2, Sn) ;
estimer la mesure de capteur de remplacement et la mesure de capteur de remplacement
respective (Ŝk) ;
filtrer au moins une mesure de capteur préalable obtenue à un moment antérieur ;
prédire la mesure de capteur de remplacement ou la mesure de capteur de remplacement
respective (Ŝk) sur la base d'un modèle de prévision et d'au moins une mesure de capteur préalable
obtenue à un moment antérieur ;
dériver la mesure de capteur de remplacement ou la mesure de capteur de remplacement
respective (Ŝk) d'une mesure de capteur superflue obtenue par un dispositif de capteur superflu
correspondant et/ou par inutilité de niveau applicatif ;
dériver la mesure de capteur de remplacement ou la mesure de capteur de remplacement
respective (Ŝk) d'au moins une mesure de capteur valide (S1, S2, Sn).
8. Système de capteur selon l'une quelconque des revendications 1 à 7, dans lequel l'unité
de données en série modifiée inclut un code de détection d'erreur (CRC), le code de
détection d'erreur (CRC) fournissant un statut de validité de l'unité de données en
série modifiée.
9. Système de capteur selon l'une quelconque des revendications 1 à 8, dans lequel l'unité
de données en série modifiée inclut au moins un code de correction d'erreur, le ou
chaque code de correction d'erreur étant associé à une mesure de capteur invalide
ou une mesure de capteur invalide respective (S1, S2, Sn), le ou chaque code de correction d'erreur pouvant être utilisé pour corriger une
erreur dans la mesure de capteur invalide correspondante (S1, S2, Sn) et/ou une erreur dans au moins un de la pluralité d'indicateurs de validité (FC51, FCS2, FCSn).
10. Procédé de fonctionnement d'un système de capteur, dans lequel le système de capteur
est pour une utilisation dans un réseau de courant continu à haute tension, le système
de capteur comprenant une pluralité de dispositifs de capteur et une unité de gestion
de capteur, chaque dispositif de capteur étant configuré pour obtenir une mesure de
capteur respective (S
1, S
2, S
n), le procédé incluant en outre l'étape consistant à générer une unité de données
en série pour une transmission à un système destinataire (C), l'unité de données en
série incluant la pluralité de mesures de capteur (S
1, S
2, S
n), l'unité de données en série incluant en outre une pluralité d'indicateurs de validité
(FC5
1, FCS
2, FCS
n), chaque indicateur de validité (FC5
1, FCS
2, FCS
n) fournissant un statut de validité individuel d'une respective de la pluralité de
mesures de capteur, le procédé étant
caractérisé en ce que l'unité de gestion de capteur évalue chaque indicateur de validité (FC5
1, FCS
2, FCS
n) pour déterminer si la mesure de capteur correspondante (S
1, S
2, S
n) est soit valide soit invalide,
et
en ce que l'unité de gestion de capteur :
génère une unité de données en série modifiée sur la base de l'unité de données en
série après que l'unité de gestion de capteur a évalué chaque indicateur de validité
(FC51, FCS2, FCSn) en réponse à la détermination qu'au moins une de la pluralité de mesures de capteur
(S1, S2, Sn) est invalide, dans lequel l'unité de données en série modifiée inclut au moins une
mesure de capteur valide (S1, S2, Sn) de l'unité de données en série ; et
transmet l'unité de données en série modifiée au système destinataire (C),
et en ce que l'unité de gestion de capteur transmet l'unité de données en série au système destinataire
(C) en réponse à l'unité de gestion de capteur déterminant qu'aucune de la pluralité
de mesures de capteur (S1, S2, Sn) n'est invalide.